The invention relates to detection and imaging, and more particularly to systems and methods for detection and imaging of two-dimensional (2D) sample arrays.
Surface plasmon resonance (SPR) is detected using a spectroscopy technique by sensing refractive index changes near the surface of a metal film. High sensitivity of refractive index changes provides a platform for the observation and quantification of chemical reactions at the metal/solution interface. The SPR technique can be used in a wide variety of chemical systems, including bio sensors.
Typically, SPR sensors employ a prism that supports a thin metal layer. The sample to be detected, such as a ligand, is immobilized on one side of the metal surface to form a modified metal surface. A reflection spectrum of the modified metal surface is measured by coupling in light and measuring the intensity of the reflected light as a function of the angle of incidence or the wavelength.
In SPR, usually a single sample is monitored at a given time. In case of multiple samples, the time required for detection increases, with the increase in the number of samples. Scanning angle SPR is typically used for scanning more than one sample. Typically, in a scanning angle SPR the intensity of the reflected light is measured as a function of the angle of incidence. The light is directed from a light source through a prism onto the modified metal surface. As the angle of incidence of the light is varied, at a particular angle, the surface plasmon resonance is observed as a sharp dip in the intensity of the light internally reflected within the prism at that particular angle of incidence. The angle of incidence at which resonance occurs is affected by the refractive index of the thin sample layer disposed on the metal film. The angle of incidence corresponding to resonance is thus a direct measure of the characteristics of the thin sample layer. Disadvantageously, the scanning angle SPR is limited over a narrow angular range. The limited angular range restricts the range of sample area and in some cases it also restricts refractive index that can be measured. In addition, some systems achieve 2D SPR imaging by mechanically scanning the light source. Lack of precision in the angular control while scanning the angular range affects the reproducibility of the SPR measurement results. Further, mechanical type of scanning increases complexity of the instrument.
Non-mechanical methods for scanning angles may have higher sensitivity, however, the SPR image frame rate is still less than the actual frame rate of the camera. This is because each point in time corresponds to single angle and scanning angle in time reduces actual frame rate.
Therefore, it is desirable to have improved systems and methods for detecting and imaging of 2D arrays of samples.